The reflection characteristics in total-internal-reflection waveguide optical switch are analysed in deteil. It is shown for the first time that there exists the phase changes of reflective modes and their relative phase difference. The results of numerical calculation indicate that the power reflectivity, reflective loss, phase change and their relative phase difference for the reflective TE mode and reflective TM mode remarkably depend on the refractive index change, the loss in switch region and the propagation angle.